Chirality; new findings (Introduction)

by David Turell , Wednesday, May 21, 2025, 17:44 (9 hours, 27 minutes ago) @ David Turell

A new study;

https://www.sciencedaily.com/releases/2025/05/250520161843.htm

"By investigating what properties these early membranes may have had, scientists can better understand how life began and evolved into the diversity of organisms we have today.

"An important feature of membranes is what they allow to pass through and what they stop from entering the cell.

"This influences which molecules are involved in the biological processes that keep cells ticking.

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"The researchers focused on a few types of molecules essential for all life: the sugars that make up the backbone of DNA and RNA and the building blocks of proteins, known as amino acids.

"The researchers were interested in these molecules not only because they are so pervasive across life, but they also twist in specific ways.

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"In biology, chirality is important for how molecules interact.

"For example, all the sugars in DNA and RNA need to have the same chirality (all be right-handed) to assemble into the backbone of a DNA or RNA strand.

"However, why life chose one chirality over the other has remained a lingering question.

"The researchers propose that early membranes may have played a key part in selecting the right-handed sugars and left-handed amino acids that all life uses today.

"They analyzed what was able to pass through membranes with properties similar to those of archaea, a major group of microbes.

"The researchers also tested a membrane they designed that mixes archaeal and bacterial properties.

"For both types of membranes, the right-handed DNA and RNA sugars more easily passed through, while the left-handed versions had trouble permeating.

"There was more variability among amino acids. Some left-handed amino acids were more likely to pass through the membrane with mixed bacterial and archaeal properties.

"This included the amino acid alanine, which is thought to be one of the first amino acids used by life.

"While this study doesn't paint a complete picture of the amino acids our cells use today, these findings demonstrate how differences in membranes strongly affect which amino acids are able to pass through.

"The authors add, "All known life uses a specific stereochemistry: left-handed amino acids and right-handed DNA. Understanding how this evolved is a long-standing mystery key for understanding the origin of life. Our experiments show that a specific type of membrane -- the structure that encloses cells -- acts as a sieve that selects for the stereochemistry life uses.'"

Comment: still no answers as to why life is so selective in uses of chirality. And it complicates studying origin of life research.